In recent years, with the arrival of a high-level information society, a large amount of data is handled by computers. Many computers are often installed in the same room in an institution such as a data center and managed collectively. Under such circumstances, a large amount of heat is produced by the computers to cause malfunction or breakdown; therefore, means for cooling the computers is used. Thus, generally in a data center, fans are used to allow heat produced inside the computers to escape to the outside of the computers, and also, the temperature of the room is adjusted by an air conditioner.
Depending on the operation statuses of the computers, the amount of heat produced by the computers fluctuates. To prevention of heat-related malfunction or breakdown of the computers, it may be conceivable to, for example, use an air conditioner having cooling capacity corresponding to the maximum amount of heat produced by the computers and constantly operate the air conditioner at its maximum capacity. However, operating the air conditioner of high cooling capacity at its maximum capacity constantly is not preferable not only because it increases running costs, but also in view of energy saving and CO2 reduction. For this reason, it is desired that air conditioning be controlled efficiently according to the amount of heat produced by each rack.
For efficient control of air conditioning, the temperature of each rack installed in the data center prefers to be measured in real time. It has conventionally been proposed to use an optical fiber as a temperature sensor for measuring a temperature distribution of an area having a plurality of heat sources, such as a data center.    Patent Document 1: Japanese Laid-open Patent Publication No. 2009-265077    Patent Document 2: Japanese Laid-open Patent Publication No. 2010-160081